PLAN OF STUDY. 



xiii 



young student, upon reading this very questionable doctrine, turn 

 to this Dictionary,* he will learn that Colonel Montagu uniformly 

 found the nests cold, and that taking into account the chemical 

 principles of fermentation, it was impossible they could be warm. 



But Pennant also mentions a circumstance of much more in- 

 terest in reference to the original inquiry, when he says that this 

 bird 44 lays five or six white eggs, and always covers them when it 

 quits the nest" — the very point to ascertain which the research 

 was begun. With this authority, supported as it is by Montagu, 

 most students might rest satisfied, but the ardent naturalist never 

 arrives at any conclusion like this, without bringing all the facts 

 within his knowledge to bear upon it, in order to elucidate con- 

 necting causes and consequences ; for the fact being ascertained 

 of the mother bird covering her eggs, it becomes interesting to 

 inquire why she does this. 



It is admitted by all the naturalists already quoted, that the 

 nest in question is built on moist ground, if not actually touching 

 the water, and that part at least of the materials consist of moist 

 water plants. Now it is indispensable to hatching, that the eggs 

 be kept at a high temperature, and not be suffered for a moment 

 to cool. The natural heat of the bird itself is sufficient for this 

 purpose, without the heat of fermentation, erroneously supposed 

 by Pennant ; but if she quits them for a moment to go in pur- 

 suit of food, or to withdraw the attention of an intruding water 

 spaniel, or a prying naturalist, their near vicinity to moist plants 

 or to water, would certainly prove fatal to the embryo chicks. 

 In order then to prevent her brood from being destroyed by cold, 

 the careful bird covers the eggs with a quantity of dry hay, to 

 keep them warm till her return. 



By keeping this interesting fact in his mind, our young natu- 

 ralist may subsequently find that other birds employ the same or 

 similar devices. The carrion-crow (Corvus corone) for example, 

 who lines her nest with wool and rabbits' fur, always covers her 

 eggs with a quantity of this before leaving her nest, no doubt for 

 the same reason that the dabchick employs hay. Again, several 

 birds of very different habits, such as the wood- wren (Sylvia sibi- 

 latrix) and the hay bird, (Sylvia trochilas,) construct a perma- 

 nent arch of moss and dried grass over their nests, leaving a nar- 



* Page 127. 



